Hello,
I’m writing to ask for some guidance regarding an issue I’m having with an indexable end mill on my PCNC 1100 when milling 6061 aluminum compounds.
Currently, I have a successful roughing routine using a serrated 30° helix 4-flute end mill:
• Depth of cut (DOC): ~2 mm
• Width of cut (WOC): ~8 mm
• Spindle speed: 5120 RPM (max)
• Feed rate: over 1000 mm/min (climb milling)
This setup works beautifully—smooth cutting with a great surface finish and no chatter.
Recently, I purchased a 12 mm diameter 3-flute indexable end mill, specified by the manufacturer for roughing:
• Helix: 10°
• Tip radius: 0.4 mm
No matter what parameters I try—reduced depth of cut (1 mm), various widths of cut (from 6 mm to full slot at 12 mm), lower spindle speeds, higher spindle speeds (up to the max of 5120 RPM), different feed rates, all in climb milling—it always results in severe chatter and a “hammering” sound. with lower feeds (under 1000mm/min) was the chatter so serious that machine stoped with Z-axis failure (milling in one Z level). I used G-Wizard and HSMAdvisor to validate my settings, but the best result I’ve found so far (1.5 mm DOC, 6 mm WOC, 5120 RPM, and around 1600 mm/min feed) still produces terrible hammering noise. After about 10 minutes, one of the inserts was torn out—presumably due to chatter.
I would be very grateful for your suggestions on the following:
1. What speeds, feeds, and engagements would you recommend for a 12 mm, 3-flute, 10° helix indexable end mill on a PCNC 1100 for 6061 aluminum?
2. Is conventional milling potentially better than climb milling in this scenario to reduce chatter?
3. Based on your experience, are indexable end mills generally unsuitable for the PCNC 1100, or is there a way to optimize their use successfully? I have even a bigger one (20mm, 5 VBD) but due to similar problems I can use it only for thin face milling, no way for shouldering.
4.
Thank you in advance for your time and expertise. Any tips or best practices you can share would be immensely helpful.
Kind regards,
T.
Missing a lot of information to make a good speed and feed recommendation. Is this a negative or positive rake endmill. Are the inserts negative or positive, etc, etc.
It definitely has a positive rake angle, though I don’t have the exact measurement. Is there any other information you need? Could you share details about the indexable end mill you’re using, as well as your functional feed rates and speeds? It might be that the PCNC 1100’s maximum RPM is 5120, whereas the optimal cutting speed for 12mm diameter 6061 aluminum is just over 8000 RPM.
I have just started using a 3/4” 3 flute APKT end mill in aluminum. I run the correct APKT 1003 aluminum insert (mirror polished). 10 degree positive rake.
I am running 0.02” to 0.04” depth of cut at various engagement , with spindle speeds of 3000 to 5000 rpm.
I do not experience any noises other than what is normally expected from an end mill in aluminum. I will say, however, that these insert mills cut wicked fast through aluminum and they save me a lot of time.
I do not know what is causing your issues, but i can say it doesn’t have anything to do with your rake or the fact that it is three flute index mill.
What insert are you using?
also, three flute for a 12mm cutter means very small inserts. Are you sure this not a high feed mill?
Dear Ed,
thank you for your answer, and apologies for the late reply — the notification email ended up in spam.
A depth of cut of 0.02–0.04″ seems quite low to me; that feels more appropriate for finishing. I was considering using the tool more for roughing, around 25% depth and 15–20% radial engagement, with 5000 RPM.
Have you also tried using indexed mills this way in 6061 aluminum? I also tried a 1″ indexed mill with five inserts specifically designed for aluminum, but for side operations (which should be ideal for aluminum roughing with a low risk of chip welding) it also seems unusable with same behavior.
P.S. I am always using inserts intended specifically for aluminum.